This invention relates to a device for the drive of a shutter cocking lever and for the transport of the film, in a camera wherein the film has a hole associated with each picture frame position, and having a film transport wheel which is coupled with the spool core.
Prior to the present invention, in devices of this nature, the film transport wheel possessed a revolving internal toothing which was constructed for engagement with a pin positioned on a lever. This pin, which extended downwardly in the internal toothing, also projected upwardly into a stationary guide curve. This guide curve controlled the duration of engagement and the route for engagement of the pin in the toothing. In this manner the lever was moved to and fro between two end positions and thus rendered the shutter cocked.
The important disadvantage inherent in this known construction resides in the fact that the lever produces to-and-fro rectilinear drive motion. This becomes disadvantageous if, besides the drive of the shutter, there also occurs at the same time a drive of a revolving element, as for example, the drive of a flash cube carrier. In another known device of this type, a slipping coupling is provided between the film transport wheel and the shutter setter. The route of the film transport is greater than the route for the tightening of the shutter cocking lever. As a result thereof, there is developed during the revolution of the film transport wheel an irregular power requirement and more specifically in this manner, the power requirement towards the end of the movement of rotation becomes greater than that at the beginning. If the shutter has already been rendered cocked and merely the rest of the film still must be transported the frictional force of the slipping coupling must be overcome and this force necessarily must be greater than the force required for the pivoting of the shutter cocking lever. The camera operator on some occasions will prematurely discontinue the actuation of the film transport wheel when the power requirement becomes greater, at which time, only the shutter has been rendered cocked and the film has not yet been transported completely. Thus, the rise in the power requirement towards the end of the movement of the film transport presents a considerable disadvantage in the power-locked coupling between film transport and film drive.
Considering this state of technology as a point of departure, the fundamental purpose of the present invention is to retain the advantages of the form-locked coupling as against the power-locked coupling, and nonetheless provide a rotating drive movement instead of a rectilinear drive movement moving to and fro for the shutter drive.